Ultem PEI: Properties, Uses & Cost Guide
Tensile data verified against MatWeb.com database & manufacturer datasheets · Last updated July 2026
Published: 2026-05-25
Polyetherimide (PEI), best known by Sabic's trade name Ultem, is an amorphous high-performance thermoplastic offering an exceptional balance of high strength, inherent flame retardancy (UL94 V-0 without additives), excellent dielectric...
Polyetherimide (PEI), best known by Sabic's trade name Ultem, is an amorphous high-performance thermoplastic offering an exceptional balance of high strength, inherent flame retardancy (UL94 V-0 without additives), excellent dielectric properties, and broad chemical resistance. Its glass transition temperature of 217°C makes it suitable for applications from -40°C cryogenic to hot-water/steam environments. It is widely used in medical devices (autoclavable surgical instrument handles), aerospace interiors (low smoke, low toxicity), electrical/electronic connectors, and semiconductor wafer handling components.
Unlike semicrystalline PEEK, PEI is amorphous—it does not have a melting point and transitions gradually through its glass transition. This provides advantages in dimensional stability (low and isotropic shrinkage) and eliminates the crystallinity-dependent properties that complicate PEEK processing. However, PEI has lower chemical resistance than PEEK (particularly to chlorinated solvents and strong bases) and lower continuous service temperature. PEI must be dried to <0.02% moisture before processing; inadequate drying causes splay, silver streaks, and part brittleness.
Reinforced grades: Ultem 2300 (30% glass fiber) increases tensile strength to 140 MPa and HDT to 210°C. Ultem 4000 series adds internal mold release for improved cycle times in high-cavitation tooling.
Recommended Applications
Ultem PEI is commonly specified for:
⚠ Not Recommended For
Ultem PEI is not recommended for:
- Strong alkali environments (NaOH, KOH — PEI degrades; use PPS or PEEK for alkaline service)
- Continuous steam exposure above 180°C (use PEEK or PAI for extreme autoclave)
- Food contact without specific FDA-compliant grade certification
Selection & Application Guide
Ultem (PEI) provides the best balance of high-temperature performance, processability, and cost among amorphous high-temperature thermoplastics. Choose Ultem when continuous service temperature up to 170°C is needed with good strength, inherent flame resistance (UL94 V-0), and transparency options. Ultem is easier to process than PEEK or Torlon and costs 60-70% less, making it the pragmatic choice when PEEK-level temperature resistance isn't required.
Real-World Applications
Ultem meets FAA flammability, smoke, and toxicity (FST) requirements for aircraft interior trim, tray tables, and ventilation ducts — replacing aluminum at 40% weight savings.
Ultem's autoclave resistance (134°C steam sterilization), rigidity, and ability to be gamma-sterilized make it standard for reusable surgical tool handles and dental instrument bodies.
Ultem's high dielectric strength, low dissipation factor, and UL94 V-0 rating without flame retardant additives make it the go-to material for high-performance electrical connectors.
Ultem's heat resistance to halogen bulb temperatures, dimensional stability, and metallization capability suit it for headlamp reflectors and fog light housings.
Processing & Cost Considerations
Manufacturing Tips
- Ultem processes at melt temperatures of 340-425°C with mold temperatures of 130-180°C — high but achievable on many standard machines with high-temperature upgrades. No post-curing is required, unlike Torlon.
- Ultem is hygroscopic and must be dried at 150°C for 4-6 hours before processing. Moisture content above 0.05% causes splay marks and reduced mechanical properties. Use a dehumidifying dryer for consistent results.
- Glass-filled Ultem (2300, 30% GF) provides 2× the stiffness and HDT of unfilled grade, but at the cost of reduced impact strength and isotropic properties. Gate design must account for fiber orientation in glass-filled grades.
Ultem costs $30-80/kg — significantly less than PEEK ($80-200/kg) and Torlon ($80-120/kg). This cost advantage, combined with easier processing (no post-cure, lower mold temperatures), makes Ultem the economical high-temperature polymer choice for most applications below 170°C. Glass-filled Ultem 2300 is 10-15% more expensive than unfilled but often eliminates the need for a more expensive polymer like PEEK.
Technical Properties
| Density | 1.27 g/cm³ |
|---|---|
| Tensile Strength | 105 MPa |
| Melting Point | N/A (Amorphous, Tg 217°C) |
| Shrinkage Rate | 0.5-0.7% |
| Flexural Modulus | 3.5 GPa |
| Hdt | 200 °C at 1.82 MPa |
| Continuous Service Temp | 170 °C |
| Tensile Modulus | 3.2 GPa |
| Yield Strength | 105 MPa |
| Elongation At Break | 10% |
Engineering Tool: Shrinkage & Cost Estimator
Calculate part weight, mold cavity dimensions accounting for shrinkage, and material cost — all locally in your browser.
Equivalents & Cross-References
| Equivalent / Alternate | Action |
|---|---|
| Sabic Ultem 1000 | |
| Ultem 2300 (30% GF) | |
| RTP 2100 Series |
Frequently Asked Questions
What is the critical drying requirement for Ultem PEI?
PEI must be dried to a moisture content below 0.02% (200 ppm) before injection molding. The recommended drying conditions are 150°C (300°F) for 4-6 hours in a desiccant dryer with a dew point of -30°C or lower. Inadequate drying is the #1 cause of processing defects in PEI—moisture hydrolyzes the polymer chains at melt temperature (350-400°C), causing splay (silver streaks), reduced mechanical properties, and brittle parts. A properly dried PEI granulate should show no moisture condensation when placed in a sealed jar and cooled.
Can Ultem replace PEEK in my application?
It depends on your temperature requirement. Ultem's continuous service temperature is 170°C vs PEEK's 260°C. If your application stays below 170°C and doesn't require PEEK's chemical resistance to aggressive solvents, Ultem provides comparable strength at roughly half the material cost with easier processing. Above 170°C, PEEK is necessary.
Is Ultem transparent?
Unfilled Ultem is amber-transparent — it transmits light with an amber tint, not water-clear like polycarbonate or acrylic. This makes it suitable for light pipes and indicators where color is acceptable. For water-clear transparency, consider polysulfone (PSU) or optical PC instead.
Can Ultem be sterilized?
Yes. Ultem withstands all common sterilization methods: steam autoclave (134°C, 18 minutes), ethylene oxide gas, gamma radiation, and dry heat. It maintains mechanical properties through hundreds of autoclave cycles, making it ideal for reusable medical devices.
What is the difference between Ultem 1000 and Ultem 2300?
Ultem 1000 is the unfilled general-purpose grade with 105 MPa tensile strength and 217°C HDT. Ultem 2300 is 30% glass-filled with 186 MPa tensile strength and 210°C HDT at 1.82 MPa. The glass-filled grade provides much higher stiffness but lower impact resistance and is opaque amber rather than translucent.
Does Ultem require flame retardant additives?
No. Ultem achieves UL94 V-0 rating inherently at 0.41mm thickness without any flame retardant additives. This is a major advantage over polycarbonate (which requires brominated additives for V-0) for aircraft interior and electrical applications where halogen-free flame resistance is specified.
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References & Industry Standards
- ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
- UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
- MatWeb. Material Property Data for Engineering Thermoplastics. matweb.com
- ISO 1043. Plastics — Symbols and Abbreviated Terms. iso.org